Apparatus for manufacturing bearings that are to be used particularly in the watchmaking industry and for small apparatuses

ABSTRACT

A thermoplastic bearing and method of making same for use particularly in the watchmaking industry and for small apparatuses wherein the bearing body is installed on the tip of an axially movable punch with the punch penetrating slightly into the inside of the body, and a piece of thermoplastic material is placed on the body which body and material are then heated until the material softens whereupon the punch together with the bearing body and thermoplastic material are moved axially toward a second punch placed coaxially and upside down with respect to the first punch so as to allow the piece of thermoplastic material to leave the heating zone just before molding, and the material between the two punches is then squeezed, the material being cooled instantaneously by contact with the second punch during molding.

United States Patent Kurucz et al.

[ 1 Aug.22, 1972 [54] APPARATUS FOR MANUFACTURING BEARINGS THAT ARE TOBE USED PARTICULARLY IN THE WATCHMAKING INDUSTRY AND FOR SMALLAPPARATUSES [72] Inventors: Janos Kurucz, Rte. Neuve 21,

Orient, Vaud; Andre Matthey, Les Jeannerets 33, Le bocle, Neuchatel,both of Switzerland [22] Filed: March 3, 1971 [21] Appl. No.: 120,646

Foreign Application Priority Data Mar. 10, l970 Switzerland ..3453/70Sept. 29, 1970 Switzerland ..14526/70 [52] US. Cl. ..425/116, 425/117,425/125, 425/ 128, 425/408, 264/268 [51] Int. Cl. ..B29c 3/00, B29c 6/00[58] Field of Search ..425/116, 117, 125, 128, 406, 425/408 [56]References Cited UNITED STATES PATENTS 569,969 10/1896 Kempshall ..425/129 2,304,190 12/ l 942 Milner ..425/408 2,559,861 7/ l 951 Kay..425/125 3,189,947 6/1965 Pettkoske ..425/ 128 3,257,709 6/1966 Fernanet al ..425/116 X Primary Examiner-J. Howard Flint, Jr. AttorneyKenwoodRoss and Chester E. Flavin [57] ABSTRACT A thermoplastic bearing andmethod of making same for use particularly in the watchmaking industryand for small apparatuses wherein the bearing body is installed on thetip of an axially movable punch with the punch penetrating slightly intothe inside of the body, and a piece of thermoplastic material is placedon the body which body and material are then heated until the materialsoftens whereupon the punch together with the bearing body andthermoplastic material are moved axially toward a second punch placedcoaxially and upside down with respect to the first punch so as to allowthe piece of thermoplastic material to leave the heating zone justbefore molding, and the material between the two punches is thensqueezed, the material being cooled instantaneously by contact with thesecond punch during molding.

8 Claims, 2 Drawing Figures PATENTED M1822 FIG.4

INVENTORS.

Ww Q e Giza/$461M ATTORNEYS.

APPARATUS FOR MANUFACTURING BEARINGS THAT ARE TO BE USED PARTICULARLYINTHE WATCHMAKING INDUSTRY AND FOR'SMALL APPARATUSES The presentinvention relatesto apparatus for manufacturing bearings that are to beused particularly in the watchmaking industry and for small apparatuses.These bearings are made of a thermoplastic material directly mouldedinto the supporting body of the bearing.

The process comprises installing the bearing body on the tip of anaxially movable punch, said punch penetrating slightly into the insideof said body, placing a piece of thermoplastic material on the body,heating body and material together until the material softens, movingsaid punch together with said bearingbody and thermoplastic materialaxially toward a second punch placed coaxially and upside down withrespecttox-the first punch, and moving allowing the piece of"thermoplastic material to leave the heating zone just before moulding,and squeezing and crushing said material between the two punches, thematerial being cooled .instantaneously be contact with the second punchduring moulding.

This device comprises a movable'punch on the tip of which is placed abearing body, heatingmeansacting on said bearing when installedover'thepunch tip and on a piece of thermoplastic material'placed uponsaid bearing body, and a second punch, facing .the first punch, locatedcoaxially with respect'to it outside of the heating zone of the heatingmeans, constructed in such a way that the heated bearing body with itsthermoplastic material is moved by simultaneously in the displacement ofthe first punch so that it leaves'the heated zone, contacts the secondpunch so that'the thermoplastic material is squeezed and moulded betweenthe two punches and .at the same time forced into the inside of thebearing body.

The invention is illustrated by the following example and theaccompanying drawings.

FIG. 1 is an axial sectional view of a device for manufacturing bearingsfor the watchmaking industry, and,

FIG. 2 is another magnified sectional view of apart of the same deviceshowing the phase of moulding.

The device, pictured schematically, comprises a frame structure boringhaving at the base .a bearing and a movable punch-bearer 3 therein. Apointed'punch is attached to the upper end of the .punch bearer.3, the

displacements of which are driven, in'the direction of the arrow 5, by amaster lever 6 located in a radial spacing 7 of the frame 1, and whichis hinged t6a.

There is a hollow spacing 8 in .the .upperpart'of the frame 1,containing an annular stationary heatingbody 9 which acts essentially ata level corresponding to the top of the punch 4 when the punch 4 is inits lower starting position as shown in FIG. 1.

The frame carries a second punch 10, unmovable, located coaxially to andfacing punch 4.

The above device operates as follows:

An annular bearing-body 11 is installed on the tip of the punch 4; whenpunch 4 is in its lower'position (-FIG. 1), the bearing-body engagesslightly into the boring of the punch bearer 3 which accommodatesithepunch 4. A piece of thermoplastic material l2,'preferablyselflubricating, is placed over the bearing-body 11 and both of theseelements, 11 and 12, are'heated together with the heater, or oven 9.

The heating temperature should be about 30 to 40 'C less then theameltingpoint of the thermoplastic material. It is therefore preferablethat the heater be regulated in such a'manner that the heatingtemperature does not go beyond the temperature at which the "plasticsimply softens, even if the punch-4 stays in its initial position longerthen necessary. Therefore, the

heating time is-not critical and the working rate needs 'notbepredetermined.

Because of internal cohesion force, the plastic material does not flowwhen r heated at the right temperature'but acquires the shape of a smallshiny sphere which remains so, as longas the heating temperature isconstant. Thischange isvisible and informs the operator of "themoment'at which he should operate master stroke, the "plastic 12 meetsthe front side of the stationary punch 10; 'itxiszthen squeezed andsquashed between the two punches and simultaneously forceshaped'intothe'body 11.

While this shaping operation is performed, .the

plastic iscooled instantaneously by contact with punch 10; so it may-be:advantageous .to choose for punch 10 a material having a thermalconductivity suited for this purpose.

The cooling rate of the plastic during moulding and themoulding'pressure are critical for obtaining, on the surface ofthe'bushin'g 12 and particularly the surfaces forming'the central holdthereof shaped by the tip of .the punch 4, a film having a harderstructure than the rest of the material.

This "film results from the cooling of the skin which exists around themolten plastic when the plastic is softened to give the shiny balldescribed above. The skin" constitutes .a"bag which is simply shaped by"punch 10;.the skin" is ruptured by the ring shaped edge 13 'bom by thefront face of punch 10, only at the moment when .this edge contacts aflanged opening 14 in theinside of bearing-bodyll.

' However already .then, thecoding effect produces a hardering of theskin" which results in the formation of the hard surface film mentionedabove which film imparts'to the bushing .12 good shock absorbing pro-:perties.

Effectively, the-structure of thematerial of the bushing is not-hardenough to prevent it fromresponding The work-up of the present processmay involve some problems resulting mainly from variations in softeningand melting points of different plastics and due to the factthatthesetemperatures 1must be carefully controlled during work-up.

For instance it has been noticed that the cooling conditions have to beaccurately controlled,.and modified when one sort of plastic is replacedby another one, otherwise the crystallization of the plastic isincomplete and the finished product is unsatisfactory its propertieschanging with age. I

The above difficulties are removed by using the following modificationof the invention The fixed punch comprised in the device of the abovementioned embodiment is provided with a heating attachment to keep it atconstant temperature during work-up, to prevent said punch from being atan improper temperature when it contacts the molten plastic. The ratiobetween the temperature of the lower punch with the bearing-body andthat of the upper punch can then be optimalized with regard to thethermoplastic material chosen.

The heating attachment to heat the upper punchcan be ring-shaped tosurround the punch and have an independent electric source. Thetemperature control can be obtained either by varying the supplyvoltage, or by an axial displacement of the heating element along thepunch, or by modifying its diameter, i. e. its distance to the punch.Evidently the same control means can be applied to the lower. punchwhich permits a fine setting of temperature ratios.

The heater of the lower punch can also be provided with a metal tubewhich extends the heating action up to the upper punch. The size and theshape of this tubular part can be chosen as a function of the desiredtemperature ratio.

Concerning said ratio, it can be said that for instance when thethermoplastic material is polyethylene terephthalate, the temperature ofthe lower punch, bearing-body and plastic can vary from 240 to 280 C,the best value being about 260 C, whereas the upper punch should bebetween 130 and 150 C, the best being around 140 C.

In the case of acetals, the lower parts temperature can be comprisedbetween 150 and 180 C, the optimum being at 160, whereas the upper partsshould be between 40 and 60 C, the best being 50 C.

It is thus possible to have very fine adjustments of the temperatureratios; this is extremely important where the manufacture ofmicro-bearing with a total volume of only a few tenth of cubicmillimeter isconcemed.

We claim: 1. Moulding device for manufacturing bearings usable in thewatchmaking industry and for small apparatuses the bushing of which ismade of a thermoplastic material directly moulded in the supporting bodyof-the bearing, which comprises a movable first punch on the tip ofwhich is placed a bearing body into which body the first punch tippenetrates, heating means acting on said bearing when installed oversaid first punch tip and on a piece of thermoplastic material placedupon said bearing-body, and a second punch facing the first punch,located coaxially with respect to said first punch 14 outside of theheating zone of the heating such a way that the heated bearing body withits thermoplastic material is moved simultaneously by the dis- 0placement of the first punch so that it leaves the heated zone, contactsthe second punch so thatthe thermoplastic material is squeezed andmoulded between the two punches andat the same time forced into theinside of the bearing body and iscooled.

2. Device as claimed in claim 1, characterized by the fact that theheating means are arranged so as to work by radiation.

3. Device as claimed in claim 1, characterized by the fact that theheating means are ring shaped and have in their center the upper end ofthe first punch when said first punch occupies one of the two extremepositions defined by its stroke.

4. Device as claimed in claim 1, characterized by the fact that itcomprises means to heat the second punch.

5. Device as claimed in claim 4, characterized by the fact that theheating means of the second punch are arranged in such a way that thetemperature of said second punch is kept constant for the full time ofthe operational cycle.

6. Device as claimed in claim 4, characterized by the fact that theheating means of the second punch are electrical means.

7. Device as claimed in claim 6, characterized by the fact that the saidelectricalheating means are axially movable along the second punch, sothat its action is means, means to displace the first punch in

1. Moulding device for manufacturing bearings usable in the watchmakingindustry and for small apparatuses the bushing of which is made of athermoplastic material directly moulded in the supporting body of thebearing, which comprises a movable first punch on the tip of which isplaced a bearing body into which body the first punch tip penetrates,heating means acting on said bearing when installed over said firstpunch tip and on a piece of thermoplastic material placed upon saidbearing-body, and a second punch facing the first punch, locatedcoaxially with respect to said first punch outside of the heating zoneof the heating means, means to displace the first punch in such a waythat the heated bearing body with its thermoplastic material is movedsimultaneously by the displacement of the first punch so that it leavesthe heated zone, contacts the second punch so that the thermoplasticmaterial is squeezed and moulded between the two punches and at the sametime forced into the inside of the bearing body and is cooled.
 2. Deviceas claimed in claim 1, characterized by the fact that the heating meansare arranged so as to work by radiation.
 3. Device as claimed in claim1, characterized by the fact that the heating means are ring shaped andhave in their center the upper end of the first punch wheN said firstpunch occupies one of the two extreme positions defined by its stroke.4. Device as claimed in claim 1, characterized by the fact that itcomprises means to heat the second punch.
 5. Device as claimed in claim4, characterized by the fact that the heating means of the second punchare arranged in such a way that the temperature of said second punch iskept constant for the full time of the operational cycle.
 6. Device asclaimed in claim 4, characterized by the fact that the heating means ofthe second punch are electrical means.
 7. Device as claimed in claim 6,characterized by the fact that the said electrical heating means areaxially movable along the second punch, so that its action iscontrollable.
 8. Device as claimed in claim 6, characterized by the factthat the said electrical heating means have a modifiable shape so thattheir heating action on the second punch be adjustable by a change ofthe distance between said heat means and said second punch.